Power amplification system with envelope-based bias

ABSTRACT

Disclosed herein are power amplification systems that are dynamically biased based on a signal indicative of an envelope of the signal being amplified. The power amplification systems include a power amplifier configured to amplify an input radio-frequency (RF) signal to generate an output RF signal when biased by a biasing signal. The power amplification systems also include a bias component configured to generate the biasing signal based on an envelope signal indicative of an envelope of the input RF signal. The biasing signal can improve or enhance the linearity of the power amplification systems.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Prov. App. No. 62/337,474 filedMay 17, 2016 and entitled “POWER AMPLIFICATION SYSTEM WITHENVELOPE-BASED BIAS,” which is expressly incorporated by referenceherein in its entirety for all purposes. This application is alsorelated to U.S. patent application Ser. No. 15/221,489 filed on Jul. 27,2016 and entitled “POWER AMPLIFICATION SYSTEM WITH PROGRAMMABLE LOADLINE,” which is expressly incorporated by reference herein in itsentirety for all purposes.

BACKGROUND Field

The present disclosure relates to power amplification systems configuredto amplify signals for wireless communication.

Description of Related Art

Power amplification systems can be used to amplify wireless signals fortransmission. These amplification systems can be powered using a supplyvoltage. The supply voltage can be varied based on an envelope of thesignal to be amplified to improve power amplifier efficiency, otherwiseknown as envelope tracking.

SUMMARY

According to a number of implementations, the present disclosure relatesto a power amplification system that includes a power amplifierconfigured to amplify an input radio-frequency (RF) signal to generatean output RF signal when biased by a biasing signal, and a biascomponent configured to generate the biasing signal based on an envelopesignal indicative of an envelope of the input RF signal.

In some embodiments, the system further includes a supply componentconfigured to generate an envelope-based supply voltage for powering thepower amplifier. In further embodiments, the biasing signal isconfigured to enhance a linearity of the power amplifier.

In some embodiments, the power amplifier includes a cascode poweramplifier including a first transistor and a second transistor. Infurther embodiments, the first transistor has a gate to receive thebiasing signal, a drain coupled to a supply voltage, and a sourcecoupled to a drain of the second transistor. In further embodiments, thesecond transistor has a gate coupled to a supplemental biasing signaland a source coupled to a ground voltage. In further embodiments, thesupplemental biasing signal is based on the envelope signal. In somefurther embodiments, the supplemental biasing signal is independent ofthe envelope signal. In some further embodiments, the input RF signal isreceived at an input RF port coupled to the gate of the secondtransistor and the output RF signal is provided at an output RF portcoupled to the drain of the first transistor. In further embodiments,the input RF port is coupled to the gate of the second transistor via aninput matching component and the output RF port is coupled to the drainof the first transistor via an output matching component.

In some embodiments, the system also includes a bias time alignmentcircuit configured to align in time the biasing signal with the envelopesignal. In further embodiments, the system also includes an envelopealignment circuit configured to align in time the biasing signal and theenvelope signal. In further embodiments, the system also includes a biasshaping circuit configured to manipulate a shape of the biasing signalto enhance linearity or efficiency of the power amplifier.

In some embodiments, the power amplifier includes a plurality of cascodeamplifiers coupled in parallel. In further embodiments, the system alsoincludes one or more switches configured to pass or block the biasingsignal to a respective one or more of the plurality of cascodeamplifiers. In further embodiments, the system also includes acontroller configured to set a respective state of the one or moreswitches based on a power output.

In a number of implementations, the present disclosure relates to aradio-frequency (RF) module that includes a packaging substrateconfigured to receive a plurality of components. The RF module alsoincludes a power amplification system implemented on the packagingsubstrate, the power amplification system including a power amplifierconfigured to amplify an input radio-frequency (RF) signal to generatean output RF signal when biased by a biasing signal and a bias componentconfigured to generate the biasing signal based on an envelope signalindicative of an envelope of the input RF signal.

In some embodiments, the power amplifier includes a cascode poweramplifier including a first transistor and a second transistor, thefirst transistor being biased by the biasing signal, the secondtransistor being biased by a supplemental biasing signal. In someembodiments, the RF module also includes a supply component implementedon the packaging substrate, the supply component configured to generatean envelope-based supply voltage for powering the power amplifier.

According to a number of implementations, the present disclosure relatesto a wireless device that includes a transceiver configured to generatea radio-frequency (RF) signal. The wireless device also includes afront-end module (FEM) in communication with the transceiver, the FEMincluding a packaging substrate configured to receive a plurality ofcomponents, the FEM further including a power amplification systemimplemented on the packaging substrate, the power amplification systemincluding a power amplifier configured to amplify an inputradio-frequency (RF) signal to generate an output RF signal when biasedby a biasing signal and a bias component configured to generate thebiasing signal based on an envelope signal indicative of an envelope ofthe input RF signal. The wireless device also includes an antenna incommunication with the FEM, the antenna configured to transmit theoutput RF signal received from the power amplification system.

For purposes of summarizing the disclosure, certain aspects, advantagesand novel features have been described herein. It is to be understoodthat not necessarily all such advantages may be achieved in accordancewith any particular embodiment. Thus, the disclosed embodiments may becarried out in a manner that achieves or optimizes one advantage orgroup of advantages as taught herein without necessarily achieving otheradvantages as may be taught or suggested herein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example wireless system or architecture having anamplification system.

FIG. 2 illustrates an example amplification system having an amplifierassembly with one or more power amplifiers.

FIGS. 3A, 3B, 3C, 3D, and 3E illustrate example implementations of poweramplifiers.

FIG. 4A illustrates an example amplification system having a poweramplifier biased by a biasing signal based on a received envelopesignal.

FIG. 4B illustrates an example amplification system having a poweramplifier biased by a biasing signal based on a received envelope signalwith additional time alignment elements.

FIG. 4C illustrates an example amplification system having a poweramplifier biased by a biasing signal based on a received envelope signalwith additional signal shaping components.

FIG. 5 illustrates an example amplification system having a powerconverter that converts a biasing signal into an envelope-based biasingsignal via an RC circuit.

FIG. 6A illustrates an example amplification system that includes acascode power amplifier.

FIG. 6B illustrates an example amplification system that includes asingle transistor.

FIG. 7A illustrates an example envelope tracker implemented as a bufferamplifier.

FIG. 7B illustrates an example envelope tracker implemented as adigital-to-analog (D/A) converter.

FIG. 8 illustrates an example power amplification configuration thatincludes an amplification system with multiple cascode amplifierscontrolled by a controller.

FIG. 9 illustrates an example amplification system that includes anon-linear device.

FIG. 10 illustrates an example module that incorporates an amplificationsystem with an envelope-based bias.

FIG. 11 illustrates an example wireless device that incorporates anamplification system with an envelope-based bias.

DETAILED DESCRIPTION OF SOME EMBODIMENTS

The headings provided herein, if any, are for convenience only and donot necessarily affect the scope or meaning of the claimed invention.

Referring to FIG. 1, one or more features of the present disclosuregenerally relate to a wireless system or architecture 50 having anamplification system 52. In some embodiments, the amplification system52 can be implemented as one or more devices, and such device(s) can beutilized in the wireless system/architecture 50. In some embodiments,the wireless system/architecture 50 can be implemented in, for example,a portable wireless device. Examples of such a wireless device aredescribed herein.

FIG. 2 shows that the amplification system 52 of FIG. 1 typicallyincludes a radio-frequency (RF) amplifier assembly 54 having one or morepower amplifiers (PAs). In the example of FIG. 2, three PAs 60 a-60 care depicted as forming the RF amplifier assembly 54. It will beunderstood that other numbers of PA(s) can also be implemented. It willalso be understood that one or more features of the present disclosurecan also be implemented in RF amplifier assemblies having other types ofRF amplifiers.

In some embodiments, the RF amplifier assembly 54 can be implemented onone or more semiconductor die, and such die can be included in apackaged module such as a power amplifier module (PAM) or a front-endmodule (FEM). Such a packaged module is typically mounted on a circuitboard associated with, for example, a portable wireless device.

The PAs (e.g., 60 a-60 c) in the amplification system 52 are typicallybiased by a bias system 56. Further, supply voltages for the PAs aretypically provided by a supply system 58. In some embodiments, either orboth of the bias system 56 and the supply system 58 can be included inthe foregoing packaged module having the RF amplifier assembly 54.

In some embodiments, the amplification system 52 can include a matchingnetwork 62. Such a matching network can be configured to provide inputmatching and/or output matching functionalities for the RF amplifierassembly 54.

For the purpose of description, it will be understood that each PA (60)of FIG. 2 can be implemented in a number of ways. FIGS. 3A-3E shownon-limiting examples of how such a PA can be configured. FIG. 3A showsan example PA having an amplifying transistor 64, where an input RFsignal (RF_in) is provided to a base of the transistor 64, and anamplified RF signal (RF_out) is output through a collector of thetransistor 64.

FIG. 3B shows an example PA having a plurality of amplifying transistors(e.g., 64 a, 64 b) arranged in stages. An input RF signal (RF_in) isprovided to a base of the first transistor 64 a, and an amplified RFsignal from the first transistor 64 a is output through its collector.The amplified RF signal from the first transistor 64 a is provided to abase of the second transistor 64 b, and an amplified RF signal from thesecond transistor 64 b is output through its collector to thereby yieldan output RF signal (RF_out) of the PA.

In some embodiments, the foregoing example PA configuration of FIG. 3Bcan be depicted as two or more stages as shown in FIG. 3C. The firststage 64 a can be configured as, for example, a driver stage; and thesecond stage 64 b can be configured as, for example, an output stage.

FIG. 3D shows that in some embodiments, a PA can be configured as aDoherty PA. Such a Doherty PA can include amplifying transistors 64 a,64 b configured to provide carrier amplification and peakingamplification of an input RF signal (RF_in) to yield an amplified outputRF signal (RF_out). The input RF signal can be split into the carrierportion and the peaking portion by a splitter. The amplified carrier andpeaking signals can be combined to yield the output RF signal by acombiner.

FIG. 3E shows that in some embodiments, a PA can be implemented in acascode configuration. An input RF signal (RF_in) can be provided to abase of the first amplifying transistor 64 a operated as a commonemitter device. The output of the first amplifying transistor 64 a canbe provided through its collector and be provided to an emitter of thesecond amplifying transistor 64 b operated as a common base device. Theoutput of the second amplifying transistor 64 b can be provided throughits collector so as to yield an amplified output RF signal (RF_out) ofthe PA.

In the various examples of FIGS. 3A-3E, the amplifying transistors aredescribed as bipolar junction transistors (BJTs) such as heterojunctionbipolar transistors (HBTs). It will be understood that one or morefeatures of the present disclosure can also be implemented in or withother types of transistors such as field-effect transistors (FETs).

FIG. 4A shows that in some embodiments, an amplification system 400 caninclude a power amplifier 420 biased by a biasing signal based on areceived envelope signal. The amplification system 400 includes a poweramplifier 420 that receives an input RF signal (RFin) at an input port401 and provides, as an output RF signal (RFout) at an output port 402,an amplified version of the input RF signal. The power amplifier 420 canbe, for example, any of the power amplifiers of FIGS. 3A-3E. In someimplementations, and as described further below, the power amplifier 420includes a cascode amplifier.

The power amplifier 420 receives an envelope-based biasing signal(VbiasE) for biasing the power amplifier 420. In particular, theenvelope-based biasing signal can bias one or more transistors of thepower amplifier 420. The envelope-based biasing signal can be, forexample, a current or a voltage. The power amplifier also receives anenvelope-based supply voltage (VccE) for powering the power amplifier420. Each of the envelope-based biasing signal and the envelope-basedsupply voltage are based on an envelope signal received by theamplification system 400 via an envelope port 405.

Accordingly, the amplification system 400 can be configured to adjust asupply voltage to the power amplifier 420 based on an envelope of the RFsignal to be amplified. This can improve efficiency of the poweramplifier 420. In addition, the amplification system is configured toadjust a bias voltage to the power amplifier 420 based on the envelopeof the RF signal to be amplified. This can improve linearity of thepower amplifier 420 in addition to providing improved efficiency.

Thus, the amplification system 400 is configured to bias the poweramplifier 420 using envelope tracking to operate the power amplifier 420so that targeted or desirable characteristics are achieved. For example,the amplification system 400 can bias the power amplifier 420 to improvelinearity of the amplification process or so that the power amplifier420 operates in a linear region. This can be done to extend the signalranges over which the power amplifier 420 provides linear amplification.

In addition, dynamic and intelligent biasing of the power amplifier 420can improve efficiency. For example, biasing the power amplifier 420using a biasing signal that varies in response to the envelope of thesignal to be amplified can extend the output range of the poweramplifier 420. For static biasing voltages or for voltages that do notvary as the signal envelope varies, a power amplifier may reach voltagelimits beyond which amplification becomes undesirably or unacceptablynon-linear (e.g., non-linearity of the amplification is outside atargeted range). Thus, by varying a bias signal to the power amplifier420, the range over which the power amplifier 420 can operateefficiently can be extended. Moreover, the power amplifier 420 can becaused to operate in a targeted linear region using such varying biassignals.

The amplification system 400 includes a power converter 410 thatreceives a supply voltage (Vcc) via a supply port 404, a biasing signal(Vbias) via a bias port 403, and an envelope signal via the envelopeport 405. The envelope signal is indicative of an envelope of the inputRF signal. In various implementations, the envelope signal is an analogsignal or a digital signal. The power converter 410 (or, in particular,a supply component 411 thereof) converts, based on the envelope signal,the supply voltage into the envelope-based supply voltage provided tothe power amplifier 420. Similarly, the power converter 410 (or, inparticular, a bias component 412 thereof) converts, based on theenvelope signal, the biasing signal into the envelope-based biasingsignal.

Thus, the amplification system 400 includes a power amplifier 420configured to amplify an input radio-frequency (RF) signal to generatean output RF signal when biased by a biasing signal (e.g., theenvelope-based biasing signal (VbiasE)). The amplification system 400further includes a bias component 412 configured to generate the biasingsignal based on an envelope signal indicative of an envelope of theinput RF signal. The amplification system 400 further includes a supplycomponent 411 configured to generate an envelope-based supply voltage(VccE) for powering the power amplifier 420.

FIG. 4B illustrates the amplification system 400 of FIG. 4A with thepower amplifier 420 biased by a biasing signal based on a receivedenvelope signal with additional time alignment elements 423, 425, 427,429. A supply timing component 423 (e.g., a time alignment circuit) canbe configured to adjust the timing (e.g., delay) the supply signal(e.g., supply voltage) received at the supply port 404. Similarly, asignal timing component 425 (e.g., a time alignment circuit) can beconfigured to adjust the timing (e.g., delay) the signal received at theinput port 401. Similarly, a bias timing component 427 (e.g., a timealignment circuit) can be configured to adjust the timing (e.g., delay)the bias voltage received at the bias port 403. Likewise, an envelopetiming component 429 (e.g., a time alignment circuit) can be configuredto adjust the timing (e.g., delay) the envelope signal received at theenvelope port 405.

The timing components 423, 425, 427, 429 (e.g., time alignment circuits)can be configured to align the RF input signal (e.g., RFin) with one ormore of the envelope signal, the bias signal (e.g., Vbias), and thesupply signal (e.g., Vcc). This can be done, for example, so that theenvelope of the supply signal delivered to the amplifier 420 is alignedwith the envelope of the signal to be amplified (e.g., RFin). Alignmentof these signals can increase power efficiency of the power amplifier420 and reduce distortions of the amplifier output signal (e.g., RFout).

The respective timing components 423, 425, 427, 429 can include delays,time shifting elements, feedback circuits, digital signal processors(DSPs), field programmable gate arrays (FPGAs), application specificintegrated circuits (ASICs) or the like to determine alignmentparameters and/or to adjust the timing of an input signal. In someembodiments, one or more of the respective timing components 423, 425,427, 429 can employ time alignment algorithms that can be implementedvia software (e.g., on DSPs), hardware (e.g., via FPGAs), or acombination of software and hardware. Further description and examplesof time alignment components and circuits are provided in U.S. Pat. No.8,718,188 entitled “Apparatus and methods for envelope tracking,” issuedMay 6, 2014; U.S. Pat. No. 8,908,797 entitled “Apparatus and method fortime alignment of an envelope tracking power amplifier,” issued Dec. 9,2014; and U.S. Pat. No. 8,514,018 entitled “Signal alignment forenvelope tracking system,” issued Aug. 20, 2013, each of which isexpressly incorporated by reference herein in its entirety.

FIG. 4C illustrates the example amplification system 400 of FIG. 4B thathas a power amplifier 420 biased by a biasing signal based on a receivedenvelope signal with additional signal shaping components 426, 428. Abias shaping component 426 (e.g., a shaping circuit) can be configuredto shape the bias signal received at the bias port 403. In someembodiments, the bias shaping component 426 can receive the bias signalprior to the bias timing component 427. Similarly, an envelope shapingcomponent 428 (e.g., a shaping circuit) can be configured to shape theenvelope signal received at the envelope port 405. In some embodiments,the envelope shaping component 428 can receive the envelope signal priorto the envelope timing component 429.

The bias shaping component 426 and the envelope shaping component 428can be configured to adjust the shape of the respective signals (e.g.,the voltage and/or current as a function of time) to enhance efficiencyand/or linearity. In some implementations, there may be a trade off whenenhancing efficiency and linearity such that, improving or optimizingone (e.g., linearity or efficiency) means that the other (e.g.,efficiency or linearity) may not be able to achieve a targetedimprovement or optimization. Accordingly, the shaping components 426,428 can shape the respective signals to preferably enhance linearityover efficiency, to enhance efficiency over linearity, or to balanceenhancements to linearity and efficiency.

In some embodiments, the shaping components 426, 428 can include one ormore lookup tables (LUTs) to determine signal shape for the respectivesignals. The LUTs can provide parameters that dictate changes oralterations to the shapes of the respective signals to achieve targetedperformance in efficiency, linearity, or a combination of these.

The shaping components 426, 428 can include, for example and withoutlimitation, analog-to-digital converters (ADCs), digital-to-analogconverters (DACs), amplifiers, delays, digital signal processors (DSPs),field programmable gate arrays (FPGAs), application specific integratedcircuits (ASICs) or the like to manipulate the shape of the respectiveinput signals to provide a targeted output signal (e.g., an output orshaped envelope signal or an output or shaped bias signal). Furtherdescription and examples of signal shaping components and circuits areprovided in U.S. Pat. No. 8,718,188 entitled “Apparatus and methods forenvelope tracking,” issued May 6, 2014, the entirety of which isexpressly incorporated herein by reference.

FIG. 5 shows that in some embodiments, an amplification system 500 caninclude a power converter 510 that converts a biasing signal into anenvelope-based biasing signal via an RC circuit 514. Thus, in someimplementations, a bias component configured to generate a biasingsignal based on an envelope signal can include an RC circuit.

Like the amplification system 400 of FIG. 4, the amplification system500 of FIG. 5 includes a power amplifier 520 that receives an input RFsignal (RFin) at an input port 501 and provides, as an output RF signal(RFout) at an output port 502, an amplified version of the input RFsignal.

The amplification system 500 includes a power converter 510 thatreceives a supply voltage (Vcc) via a supply port 504, a biasing signal(Vbias) via a bias port 503, and an envelope signal via an envelope port505. The power converter 510 converts, based on the envelope signal, thesupply voltage into the envelope-based supply voltage provided to thepower amplifier 520. Similarly, the power converter 510 converts, basedon the envelope signal, the biasing signal into the envelope-basedbiasing signal.

In some embodiments, and as shown in FIG. 5, the power converter 510includes an envelope tracker 513 that tracks the envelope signal and/orprovides a filtered or otherwise processed version of the envelopesignal. Examples of such an envelope tracker 513 are described in detailbelow. The envelope tracker 513 can include, for example, a comparator(which can be implemented as an operational amplifier or otherdifferential amplifier) and one or more passive devices (e.g., resistorsand/or capacitors). In some implementations, the power converter 510 maynot include an envelope tracker and can receive the envelope signal viathe envelope port 505 in an appropriately filtered or otherwiseprocessed form.

The power converter 510 includes an LC combiner that combines the outputof the envelope tracker 513 and the supply voltage (Vcc) to form theenvelope-based supply voltage (VccE). The LC combiner includes aninductor 511 coupled between the supply port 504 and the envelope-basedsupply input of the power amplifier 520. The LC combiner furtherincludes a capacitor 512 coupled between the output of the envelopetracker 513 and the envelope-based supply input of the power amplifier520. Thus, in some implementations, the envelope-based supply voltage isthe combination of the envelope signal received via the envelope port513 (or a tracked version of the envelope signal) and the supply voltagereceived via the supply port 504.

The power converter 510 includes an RC circuit 514 coupled between thebias port 503 and the envelope-based bias input of the power amplifier520. The RC circuit 514 is further coupled to the output of the envelopetracker 513 via the capacitor 512 and coupled to the supply port 504 viathe inductor 511. The RC circuit can include one or more resistorsand/or one or more capacitors.

FIG. 6A shows that in some embodiments, an amplification system 600 caninclude a cascode power amplifier. The amplification system 600 receivesan input RF signal (RFin) via an input port 601 and provides, as anoutput RF signal (RFout) at an output port 602, an amplified version ofthe input RF signal. The amplification system 600 includes a bias port603 for receiving a biasing signal to at least partially bias thecascode power amplifier (or one or more transistors 671, 672 thereof).The amplification system 600 includes a supply port 604 for receiving asupply voltage to power the cascode power amplifier. The amplificationsystem 600 includes an envelope port 605 for receiving an envelopesignal indicative of an envelope of the input RF signal.

The amplification system 600 includes a cascode amplifier in the form ofa first transistor 671 and a second transistor 672. The first transistor671 is configured as a common-base stage of the cascode amplifier andthe second transistor 672 is configured as a common-emitter stage of thecascode amplifier.

Although the first transistor 671 and second transistor 672 aredescribed herein as field-effect transistors (FETs), it will beunderstood that the transistors described herein may be implemented asother types of transistors, such as bipolar junction transistors (BJTs)(e.g., heterojunction bipolar transistors (HBTs)). Similarly, the use ofparticular terms, such as “gate”, “drain”, or “source” should not betaken to imply a particular transistor type, and should be consideredinterchangeable with other terms (such as “base”, “collector”, or“emitter”) typically used to refer to other types of transistors.

The second transistor 672 has a gate coupled to the input port 601 viaan input matching component 631 and a capacitor. The gate of the secondtransistor 672 is also coupled to the bias port 603 via a resistor 662.The capacitor 661 and the resistor 662 act as an RC combiner thatcombines that biasing signal (Vbias) and the matched input RF signal(RFin).

The second transistor 672 has a source coupled to a ground voltage and adrain coupled to an intermediate cascode node 699. The intermediatecascode node 699 may optionally be coupled to the ground voltage via acapacitor 653.

The first transistor 671 has a source coupled to the intermediatecascode node 699 and a drain coupled, via an output matching component632, to the output port 602. The input matching component 631 and outputmatching component 632 can provide impedance matching functionality forthe amplification system 600.

The drain of the first transistor 671 is coupled via an inductor 621 toan envelope-based supply node 698. The envelope-based supply node 698 iscoupled, via an inductor 611, to the supply port 604 and is coupled, viaa capacitor 612, to the output of an envelope tracker 613. The envelopetracker 613 receives the envelope signal via the envelope port 605 andprovides a filtered or otherwise processed version of the envelopesignal. The capacitor 612 and the inductor 611 act as an LC combinerthat combines the processed envelope signal and the supply voltage toprovide an envelope-based supply voltage at the envelope-based supplynode 698.

The envelope-based supply node 698 and the intermediate cascode node 699can be coupled by a resistor 644.

The envelope-based supply node 698 is coupled the ground voltage via apair of resistors 641, 642. The pair of resistors 641, 642 act as avoltage divider, such that the voltage at a divided node 697 between thetwo resistors 641, 642 is approximately proportional to the voltage atthe envelope-based supply node 698. In particular, the pair of resistorsincludes a resistor 641 coupled between the envelope-based supply node698 and the divided node 697 and a resistor 642 coupled between thedivided node 697 and the ground voltage. In various implementations, thepair of resistors 641, 642 can be replaced with another voltage divider.

The gate of the first transistor 671 is coupled to the divided node 697.Thus, the first transistor 671 is biased by the voltage at the dividednode 697. In various implementations, the gate of the first transistor671 is coupled to the ground voltage via a decoupling capacitor 652which may act as an acceleration capacitor. In various implementations,the gate of first transistor 671 is coupled to the gate of the secondtransistor 672 via an impedance. As shown in FIG. 6A, such an impedancecan include a resistor 643 and/or a capacitor 651.

Thus, in various implementations, the cascode power amplifier is biasedby a voltage based on the envelope signal, e.g., the first transistor671 is biased by the voltage at the divided node 697. Further, thecascode power amplifier is powered by a voltage based on the envelopesignal, e.g., the cascode amplifier is powered by the voltage at theenvelope-based supply node 698.

As described above, the cascode power amplifier include a firsttransistor 671 and a second transistor 672. The first transistor 671 hasa gate to receive a biasing signal (e.g., is coupled to the divided node697 and receives the envelope-based biasing signal at the divided node697). The first transistor has a drain coupled to a supply voltage(e.g., is coupled to the envelope-based supply node 698 and receives theenvelope-based supply voltage at the envelope-based supply node 698).The first transistor has a source coupled to the drain of the secondtransistor 672.

The second transistor 672 has a gate coupled to a supplemental biasingsignal (e.g., the biasing signal received at the bias port 603 asinfluenced by the remainder of the amplification system) and a sourcecoupled to the ground voltage.

In some implementations, the supplemental biasing signal is based on theenvelope signal. For example, when the impedance between the gate of thefirst transistor 671 and the gate of the second transistor 672 has asmall capacitance, the voltage at the gate of the second transistor 672can be influenced by the voltage at the gate of the first transistor,which is based on the envelope signal.

In some implementations, the supplemental biasing signal is independentof the envelope signal. For example, when the impedance between the gateof the first transistor 671 and the gate of the second transistor 672has a large capacitance (or such an impedance is absent, resulting in anopen circuit between the two gates), the voltage at the gate of thesecond transistor 672 is not influenced by the envelope signal.

The various impedances shown in FIG. 6A (or subsets thereof) form a biascomponent that generates a biasing signal (e.g., the voltage at the gateof the first transistor 671) based on the envelope signal (received atthe envelope port 605).

As shown in FIG. 6A, such a bias component can include an RC circuit,such as the RC circuit formed by the pair of resistors 641, 642 and thedecoupling capacitor 652. Such a bias component can include an envelopetracker configured to provide a processed version of the envelopesignal, such as the envelope tracker 613. Such a bias component caninclude the decoupling capacitor 652 coupled between the gate of thefirst transistor 671 and the ground voltage. Such a bias component caninclude a resistor (e.g., the resistor 644) coupled between a first nodedisposed between the first transistor 671 and the second transistor 672(e.g., the intermediate cascode node 699) and a second node at a supplyvoltage of the power amplifier (e.g., the envelope-based supply node698). Such a bias component can include a pair of impedances (such asthe pair of resistors 641, 642) configured as a voltage divider, thepair of impedances including a first impedance coupled between the gateof the first transistor 671 and a ground voltage and a second impedancecoupled between the gate of the first transistor 671 and a supplyvoltage of the power amplifier (e.g., at the envelope-based supply node698). Such a bias component can include an impedance coupled between thegate of the first transistor 671 and the gate of the second transistor672. In various implementations, the impedance can include a resistorand a capacitor coupled in series (e.g., the resistor 643 and thecapacitor 651). Such a bias component can include a capacitor (e.g., thecapacitor 653) coupled between a ground voltage and a node disposedbetween the first transistor 671 and the second transistor 672 (e.g.,the intermediate cascode node 699).

FIG. 6B shows that in some implementations, an amplification system 690can include a single transistor 672. The amplification system 690 ofFIG. 6B includes many of the same components as the amplification system600 of FIG. 6A, but excludes some of the components of the amplificationsystem 600 of FIG. 6A. In particular, the amplification system 690 ofFIG. 6B includes only a single transistor 672, rather than a cascodepower amplifier including two transistors. Further, the amplificationsystem 690 of FIG. 6B includes only a single inductor 621, rather thantwo inductors coupling the supply port 604 to the output port 602.

FIG. 7A shows that in some implementations, an envelope tracker 713 canbe implemented as a buffer amplifier. The envelope tracker 713 includesan input that receives an envelope signal (Ein) and provided a processedenvelope signal (Eout). The envelope tracker 710 includes a differentialamplifier 710 (which may be implemented, for example, as an operationalamplifier) having a non-inverting input coupled to the input of theenvelope tracker 713 and an inverting input coupled to the output of theenvelope tracker 713 via a resistor 721. The inverting input is furthercoupled to a ground voltage via a resistor 722. The output of thedifferential amplifier 710 is coupled to the output of the envelopetracker 713.

FIG. 7B shows that in some implementations, an envelope tracker 753 canbe implemented as a digital-to-analog (D/A) converter. The envelopetracker 753 receives a first one-bit digital signal (B0) via a firstresistor 751 and a second one-bit digital signal (B1) via a secondresistor 752. The second resistor 752 may be twice the resistance of thefirst resistor 751. In some implementations, the envelope tracker 753receives additional one-bit signals (e.g., Bm) via additional resistors(e.g., resistor 759). In some implementations, the envelope signal is aone-bit signal received via a single terminal, a two-bit signal receivedvia two terminals, or a three-or-more-bit signal received via three ormore terminals. Thus, the digital envelope signal received by theenvelope tracker 753 can include two or more concurrent digital signals.

The digital envelope signals are fed to an amplifier 759 to effect adigital-to-analog conversion. The output of the amplifier 759 is fedback to the input via a low-pass RC filter including a RC resistor 755and an RC capacitor 756 connected in parallel. The output of theamplifier 759 provides an envelope tracking signal that may be combinedwith a supply voltage (e.g., via an LC combiner) as shown in, e.g., FIG.6A to power a power amplifier. Thus, the envelope tracking signal isgenerated by a digital-to-analog conversion of a digital envelopesignal.

FIG. 8 shows that in some embodiments, a power amplificationconfiguration 800 can include an amplification system 810 with multiplecascode amplifiers controlled by a controller 890. The amplificationsystem 810 receives an input RF signal (RFin) via an input port 801 andprovides, as an output RF signal (RFout) at an output port 802, anamplified version of the input RF signal. The amplification system 810includes a bias port 803 for receiving a biasing signal to bias one ormore power amplifiers (or one or more transistors thereof) and multiplecontrol ports 806 a-806 b for activating or deactivating the cascodeamplifiers. The amplification system 800 includes a supply port 804 forreceiving a supply voltage to power the amplification system 810. Theamplification system 810 includes an envelope port 805 for receiving anenvelope signal.

The amplification system 810 includes a plurality of cascode amplifiers,each formed by a respective first transistor 871 a-871 c and arespective second transistor 872 a-872 c. Each of the first transistors871 a-871 c is configured as a common-base stage of its respectivecascode amplifier and each of the second transistors 872 a-872 c isconfigured as a common-emitter stage of its respective cascodeamplifier.

Each of the second transistors 872 a-872 c has a gate coupled to theinput port 801 via an input matching component 831 and a capacitor 861.The gate of each of the second transistors 872 a-872 c is also coupledto the bias port 803 via a resistor 862. The capacitor 861 and theresistor 862 act as an RC combiner that combines that biasing signal(Vbias) and the matched input RF signal (RFin).

Each of the second transistors 872 a-872 c has a source coupled to aground voltage and a drain coupled to a respective intermediate cascodenode 899 a-899 c. Each of the intermediate cascode nodes 899 a-899 c mayoptionally be coupled to the ground voltage via a respective capacitor(not shown).

Each of the first transistors 871 a-871 c has a source coupled to therespective intermediate cascode node 899 a-899 c and a drain coupled,via an output matching component 832, to the output port 802. The inputmatching component 831 and output matching component 832 can provideimpedance matching functionality for the amplification system 810.

As shown in FIG. 8, the respective drain of each of the firsttransistors 871 a-871 c is coupled, via an inductor 821 to anenvelope-based supply node 898. In some embodiments, the drains of thefirst transistors 871 a-871 c are coupled via respective inductors tothe envelope-based supply node 898.

The envelope-based supply node 898 is coupled, via an inductor 811, tothe supply port 804 and is coupled, via a capacitor 812, to the outputof an envelope tracker 813. The envelope tracker 813 receives theenvelope signal via the envelope port 805 and provides a filtered orotherwise processed version of the envelope signal. The capacitor 812and the inductor 811 act as an LC combiner that combines the processedenvelope signal and the supply voltage to provide an envelope-basedsupply voltage at the envelope-based supply node 898.

The envelope-based supply node 898 and the intermediate cascode nodes899 a-899 c can be coupled by respective resistors 844 a-844 c. Further,the intermediate cascode nodes 899 a-899 c and the ground voltage can becoupled by respective resistors 844 d-844 f. Thus, the envelope-basesupply node 898 is coupled to the ground voltage via (at least) threepairs of resistors 844 a-844 f.

The envelope-based supply node 898 is further coupled the ground voltagevia another pair of resistors 841, 842. The pair of resistors 841, 842act as a voltage divider, such that the voltage at a divided node 897between the two resistors 841, 842 is less than the voltage at theenvelope-based supply node 898. In particular, the pair of resistorsincludes a resistor 841 coupled between the envelope-based supply node898 and the divided node 897 and a resistor 842 coupled between thedivided node 897 and the ground voltage. In general, each of theresistors, capacitors, and inductors described herein (with respect toFIG. 8 and other figures) can be replaced with different impedancesincluding one or more resistors, capacitors, and/or inductors.

The respective gates of the each of the first transistors 871 a-871 care coupled to the divided node 897. As shown in FIG. 8, the gate of oneof the first transistors 871 a is coupled directly to the divided node897 and the gates of the other first transistors 871 b, 871 c arecoupled to the divided node 897 via respective switches 891 b, 891 c. Insome embodiments, each of the gates of the first transistors 871 a-871 care coupled to the divided node 897 via respective switches. Theswitches 891 b, 891 c can be controlled by the controller 890 to be inan open state or a closed state.

The controller 890 can determine which of the switches to place in theopen state or the closed state by comparing a received desired outputpower signal (Pout) with an actual output power measured by a coupler894 at the output port 802 of the amplification system 810 (e.g.,coupled between the output port 802 of the amplification system 810 andan antenna 840). In various implementations, the controller is poweredby voltage from a battery (Vbatt) and can generate the biasing signal(Vbias) using this voltage.

Thus, when its respective switch is in the closed state, each firsttransistor 871 a-871 c is biased by the voltage at the divided node 897.In various implementations, the divided node 897 is coupled to theground voltage via a capacitor 852 which may act as an accelerationcapacitor. In various implementations, the divided node 897 is coupledto the gate of each of the second transistors 872 a-872 c via animpedance. As shown in FIG. 8, such an impedance can include a resistor843 and/or a capacitor 851.

Thus, in various implementations, each of the cascode power amplifiers(when switched on by the controller 890) is biased by a voltage based onthe envelope signal, e.g., the respective first transistor 871 a-871 cis biased by the voltage at the divided node 897. Further, each of thecascode power amplifiers is powered by a voltage based on the envelopesignal, e.g., each of the cascode amplifiers is powered by the voltageat the envelope-based supply node 898.

FIG. 9 shows that in some embodiments, an amplification system 900 caninclude a non-linear device 982. The amplification system 900 receivesan input RF signal (RFin) via an input port 901 and provides, as anoutput RF signal (RFout) at an output port 902, an amplified version ofthe input RF signal. The amplification system 900 includes a bias port903 for receiving a biasing signal to bias a power amplifier (or one ormore transistors thereof). The amplification system 900 includes asupply port 904 for receiving a supply voltage to power theamplification system 900. The amplification system 900 includes envelopeports 905 a, 905 b for receiving a differential envelope signal.

The amplification system 900 includes a cascode amplifier in the form ofa first transistor 971 and a second transistor 972. The first transistor971 is configured as a common-base stage of the cascode amplifier andthe second transistor 972 is configured as a common-emitter stage of thecascode amplifier.

The second transistor 972 has a gate coupled to the input port 901 viaan input matching component 931 and a capacitor 961. The gate of thesecond transistor 972 is also coupled to the bias port 903 via aresistor 962. The capacitor 961 and the resistor 962 act as an RCcombiner that combines that biasing signal (Vbias) and the matched inputRF signal (RFin).

The second transistor 972 has a source coupled to a ground voltage and adrain coupled to an intermediate cascode node 999. The intermediatecascode node 999 may optionally be coupled to the ground voltage via acapacitor 953.

The first transistor 971 has a source coupled to the intermediatecascode node 999 and a drain coupled, via an output matching component932, to the output port 902. The input matching component 931 and outputmatching component 932 can provide impedance matching functionality forthe amplification system 900.

The drain of the first transistor 971 is coupled via an inductor 921 toan envelope-based supply node 998. The envelope-based supply node 998 iscoupled, via an inductor 911, to the supply port 904 and is coupled, viaa capacitor 912, to the output of an envelope tracker 913. Theenvelope-based supply node 998 is further coupled, via a capacitor 952,to ground. The envelope tracker 913 receives the envelope signal via theoutput of a differential amplifier 959 coupled to the envelope ports 605a, 605 b and provides a filtered or otherwise processed version of theenvelope signal. The capacitor 912 and the inductor 911 act as an LCcombiner that combines the processed envelope signal and the supplyvoltage to provide an envelope-based supply voltage at theenvelope-based supply node 998.

The envelope signal is also output from a second differential amplifier958 through a processing chain to the gate of the first transistor 971.The processing chain includes a delay component 981, a non-linear device982, and a buffer 983. The non-linear device 982 can provide an outputvoltage that is a non-linear function of the input voltage (a delayedversion of the envelope signal).

Thus, in various implementations, the cascode power amplifier is biasedby a voltage based on the envelope signal, e.g., the first transistor971 is biased by the voltage from the buffer 983 (a non-linearlyprocessed and delayed version of the envelope signal). Further, thecascode power amplifier is powered by a voltage based on the envelopesignal, e.g., the cascode amplifier is powered by the voltage at theenvelope-based supply node 998.

FIG. 10 shows that in some embodiments, some or all of poweramplification systems (e.g., those shown in FIGS. 5, 6A, 6B, 8, and 9)can be implemented, wholly or partially, in a module. Such a module canbe, for example, a front-end module (FEM). In the example of FIG. 10, amodule 200 can include a packaging substrate 202, and a number ofcomponents can be mounted on such a packaging substrate. For example, anFE-PMIC (Front-end Power Management Integrated Circuit) component 204, apower amplifier assembly 206, a match component 208, and a duplexerassembly 210 can be mounted and/or implemented on and/or within thepackaging substrate 202. The power amplifier assembly 206 can include anenvelope-based bias component 207 such as those described above withrespect to FIGS. 5, 6A, 6B, 8, and 9. Other components such as a numberof SMT (surface-mount technology) devices 214 and an antenna switchmodule (ASM) 212 can also be mounted on the packaging substrate 202.Although all of the various components are depicted as being laid out onthe packaging substrate 202, it will be understood that somecomponent(s) can be implemented over other component(s).

In some implementations, a device and/or a circuit having one or morefeatures described herein can be included in an RF device such as awireless device. Such a device and/or a circuit can be implementeddirectly in the wireless device, in a modular form as described herein,or in some combination thereof. In some embodiments, such a wirelessdevice can include, for example, a cellular phone, a smart-phone, ahand-held wireless device with or without phone functionality, awireless tablet, etc.

FIG. 11 depicts an example wireless device 300 having one or moreadvantageous features described herein. In the context of a modulehaving one or more features as described herein, such a module can begenerally depicted by a dashed box 200, and can be implemented as, forexample, a front-end module (FEM).

Referring to FIG. 11, power amplifiers (PAs) 320 can receive theirrespective RF signals from a transceiver 310 that can be configured andoperated in known manners to generate RF signals to be amplified andtransmitted, and to process received signals. The transceiver 310 isshown to interact with a baseband sub-system 308 that is configured toprovide conversion between data and/or voice signals suitable for a userand RF signals suitable for the transceiver 310. The transceiver 310 canalso be in communication with a power management component 306 that isconfigured to manage power for the operation of the wireless device 300.Such power management can also control operations of the basebandsub-system 308 and the module 200.

The baseband sub-system 308 is shown to be connected to a user interface302 to facilitate various input and output of voice and/or data providedto and received from the user. The baseband sub-system 308 can also beconnected to a memory 304 that is configured to store data and/orinstructions to facilitate the operation of the wireless device, and/orto provide storage of information for the user.

In the example wireless device 300, outputs of the PAs 320 are shown tobe matched (via respective match circuits 322) and routed to theirrespective duplexers 324. Such amplified and filtered signals can berouted to an antenna 316 through an antenna switch 314 for transmission.In some embodiments, the duplexers 324 can allow transmit and receiveoperations to be performed simultaneously using a common antenna (e.g.,216). In FIG. 11, received signals are shown to be routed to “Rx” paths(not shown) that can include, for example, a low-noise amplifier (LNA).

A number of other wireless device configurations can utilize one or morefeatures described herein. For example, a wireless device does not needto be a multi-band device. In another example, a wireless device caninclude additional antennas such as diversity antenna, and additionalconnectivity features such as Wi-Fi, Bluetooth, and GPS.

The present disclosure describes various features, no single one ofwhich is solely responsible for the benefits described herein. It willbe understood that various features described herein may be combined,modified, or omitted, as would be apparent to one of ordinary skill.Other combinations and sub-combinations than those specificallydescribed herein will be apparent to one of ordinary skill, and areintended to form a part of this disclosure. Various methods aredescribed herein in connection with various flowchart steps and/orphases. It will be understood that in many cases, certain steps and/orphases may be combined together such that multiple steps and/or phasesshown in the flowcharts can be performed as a single step and/or phase.Also, certain steps and/or phases can be broken into additionalsub-components to be performed separately. In some instances, the orderof the steps and/or phases can be rearranged and certain steps and/orphases may be omitted entirely. Also, the methods described herein areto be understood to be open-ended, such that additional steps and/orphases to those shown and described herein can also be performed.

Some aspects of the systems and methods described herein canadvantageously be implemented using, for example, computer software,hardware, firmware, or any combination of computer software, hardware,and firmware. Computer software can comprise computer executable codestored in a computer readable medium (e.g., non-transitory computerreadable medium) that, when executed, performs the functions describedherein. In some embodiments, computer-executable code is executed by oneor more general purpose computer processors. A skilled artisan willappreciate, in light of this disclosure, that any feature or functionthat can be implemented using software to be executed on a generalpurpose computer can also be implemented using a different combinationof hardware, software, or firmware. For example, such a module can beimplemented completely in hardware using a combination of integratedcircuits. Alternatively or additionally, such a feature or function canbe implemented completely or partially using specialized computersdesigned to perform the particular functions described herein ratherthan by general purpose computers.

Multiple distributed computing devices can be substituted for any onecomputing device described herein. In such distributed embodiments, thefunctions of the one computing device are distributed (e.g., over anetwork) such that some functions are performed on each of thedistributed computing devices.

Some embodiments may be described with reference to equations,algorithms, and/or flowchart illustrations. These methods may beimplemented using computer program instructions executable on one ormore computers. These methods may also be implemented as computerprogram products either separately, or as a component of an apparatus orsystem. In this regard, each equation, algorithm, block, or step of aflowchart, and combinations thereof, may be implemented by hardware,firmware, and/or software including one or more computer programinstructions embodied in computer-readable program code logic. As willbe appreciated, any such computer program instructions may be loadedonto one or more computers, including without limitation a generalpurpose computer or special purpose computer, or other programmableprocessing apparatus to produce a machine, such that the computerprogram instructions which execute on the computer(s) or otherprogrammable processing device(s) implement the functions specified inthe equations, algorithms, and/or flowcharts. It will also be understoodthat each equation, algorithm, and/or block in flowchart illustrations,and combinations thereof, may be implemented by special purposehardware-based computer systems which perform the specified functions orsteps, or combinations of special purpose hardware and computer-readableprogram code logic means.

Furthermore, computer program instructions, such as embodied incomputer-readable program code logic, may also be stored in a computerreadable memory (e.g., a non-transitory computer readable medium) thatcan direct one or more computers or other programmable processingdevices to function in a particular manner, such that the instructionsstored in the computer-readable memory implement the function(s)specified in the block(s) of the flowchart(s). The computer programinstructions may also be loaded onto one or more computers or otherprogrammable computing devices to cause a series of operational steps tobe performed on the one or more computers or other programmablecomputing devices to produce a computer-implemented process such thatthe instructions which execute on the computer or other programmableprocessing apparatus provide steps for implementing the functionsspecified in the equation(s), algorithm(s), and/or block(s) of theflowchart(s).

Some or all of the methods and tasks described herein may be performedand fully automated by a computer system. The computer system may, insome cases, include multiple distinct computers or computing devices(e.g., physical servers, workstations, storage arrays, etc.) thatcommunicate and interoperate over a network to perform the describedfunctions. Each such computing device typically includes a processor (ormultiple processors) that executes program instructions or modulesstored in a memory or other non-transitory computer-readable storagemedium or device. The various functions disclosed herein may be embodiedin such program instructions, although some or all of the disclosedfunctions may alternatively be implemented in application-specificcircuitry (e.g., ASICs or FPGAs) of the computer system. Where thecomputer system includes multiple computing devices, these devices may,but need not, be co-located. The results of the disclosed methods andtasks may be persistently stored by transforming physical storagedevices, such as solid state memory chips and/or magnetic disks, into adifferent state.

Unless the context clearly requires otherwise, throughout thedescription and the claims, the words “comprise,” “comprising,” and thelike are to be construed in an inclusive sense, as opposed to anexclusive or exhaustive sense; that is to say, in the sense of“including, but not limited to.” The word “coupled”, as generally usedherein, refers to two or more elements that may be either directlyconnected, or connected by way of one or more intermediate elements.Additionally, the words “herein,” “above,” “below,” and words of similarimport, when used in this application, shall refer to this applicationas a whole and not to any particular portions of this application. Wherethe context permits, words in the above Detailed Description using thesingular or plural number may also include the plural or singular numberrespectively. The word “or” in reference to a list of two or more items,that word covers all of the following interpretations of the word: anyof the items in the list, all of the items in the list, and anycombination of the items in the list. The word “exemplary” is usedexclusively herein to mean “serving as an example, instance, orillustration.” Any implementation described herein as “exemplary” is notnecessarily to be construed as preferred or advantageous over otherimplementations.

The disclosure is not intended to be limited to the implementationsshown herein. Various modifications to the implementations described inthis disclosure may be readily apparent to those skilled in the art, andthe generic principles defined herein may be applied to otherimplementations without departing from the spirit or scope of thisdisclosure. The teachings of the invention provided herein can beapplied to other methods and systems, and are not limited to the methodsand systems described above, and elements and acts of the variousembodiments described above can be combined to provide furtherembodiments. Accordingly, the novel methods and systems described hereinmay be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the methods andsystems described herein may be made without departing from the spiritof the disclosure. The accompanying claims and their equivalents areintended to cover such forms or modifications as would fall within thescope and spirit of the disclosure.

What is claimed is:
 1. A power amplification system comprising: a poweramplifier configured to amplify an input radio-frequency (RF) signal togenerate an output RF signal when biased by a biasing signal; and a biascomponent configured to generate the biasing signal based on an envelopesignal indicative of an envelope of the input RF signal.
 2. The poweramplification system of claim 1 further comprising a supply componentconfigured to generate an envelope-based supply voltage for powering thepower amplifier.
 3. The power amplification system of claim 2 whereinthe biasing signal is configured to enhance a linearity of the poweramplifier.
 4. The power amplification system of claim 1 wherein thepower amplifier includes a cascode power amplifier including a firsttransistor and a second transistor.
 5. The power amplification system ofclaim 4 wherein the first transistor has a gate to receive the biasingsignal, a drain coupled to a supply voltage, and a source coupled to adrain of the second transistor.
 6. The power amplification system ofclaim 5 wherein the second transistor has a gate coupled to asupplemental biasing signal and a source coupled to a ground voltage. 7.The power amplification system of claim 6 wherein the supplementalbiasing signal is based on the envelope signal.
 8. The poweramplification system of claim 6 wherein the supplemental biasing signalis independent of the envelope signal.
 9. The power amplification systemof claim 4 wherein the input RF signal is received at an input RF portcoupled to the gate of the second transistor and the output RF signal isprovided at an output RF port coupled to the drain of the firsttransistor.
 10. The power amplification system of claim 7 wherein theinput RF port is coupled to the gate of the second transistor via aninput matching component and the output RF port is coupled to the drainof the first transistor via an output matching component.
 11. The poweramplification system of claim 1 further comprising a bias time alignmentcircuit configured to align in time the biasing signal with the envelopesignal.
 12. The power amplification system of claim 11 furthercomprising an envelope alignment circuit configured to align in time thebiasing signal and the envelope signal.
 13. The power amplificationsystem of claim 12 further comprising a bias shaping circuit configuredto manipulate a shape of the biasing signal to enhance linearity orefficiency of the power amplifier.
 14. The power amplification system ofclaim 1 wherein the power amplifier includes a plurality of cascodeamplifiers coupled in parallel.
 15. The power amplification system ofclaim 14 further comprising one or more switches configured to pass orblock the biasing signal to a respective one or more of the plurality ofcascode amplifiers.
 16. The power amplification system of claim 15further comprising a controller configured to set a respective state ofthe one or more switches based on a power output.
 17. A radio-frequency(RF) module comprising: a packaging substrate configured to receive aplurality of components; and a power amplification system implemented onthe packaging substrate, the power amplification system including apower amplifier configured to amplify an input radio-frequency (RF)signal to generate an output RF signal when biased by a biasing signaland a bias component configured to generate the biasing signal based onan envelope signal indicative of an envelope of the input RF signal. 18.The RF module of claim 17 wherein the power amplifier includes a cascodepower amplifier including a first transistor and a second transistor,the first transistor being biased by the biasing signal, the secondtransistor being biased by a supplemental biasing signal.
 19. The RFmodule of claim 17 further comprising a supply component implemented onthe packaging substrate, the supply component configured to generate anenvelope-based supply voltage for powering the power amplifier.
 20. Awireless device comprising: a transceiver configured to generate aradio-frequency (RF) signal; a front-end module (FEM) in communicationwith the transceiver, the FEM including a packaging substrate configuredto receive a plurality of components, the FEM further including a poweramplification system implemented on the packaging substrate, the poweramplification system including a power amplifier configured to amplifyan input radio-frequency (RF) signal to generate an output RF signalwhen biased by a biasing signal and a bias component configured togenerate the biasing signal based on an envelope signal indicative of anenvelope of the input RF signal; and an antenna in communication withthe FEM, the antenna configured to transmit the output RF signalreceived from the power amplification system.